Rocket Science and Art Restoration

NASA's trick for saving great paintings

Art Conservator Ellen Baxter was baffled. The morning after a gala exhibition opening at Pittsburgh's Andy Warhol Museum, she discovered someone had planted a kiss on a vintage Warhol painting "Bathtub" and left behind a full-lipped imprint of bright red lipstick. "My first thought was, 'Why would anyone kiss a bathtub?'" says Baxter. "I could understand if they kissed one of the Warhol images of Marilyn or Elvis or Jackie. But a bathtub?" Baxter's second thought was that the museum probably wouldn't be able to restore "Bathtub" because Warhol hadn't sealed the surface of the painting with a protective coat of varnish. Using conventional solvents would only dissolve the lipstick and allow it to permeate even farther into the chalky, porous canvas beneath, leaving a permanent and unsightly pink stain. "This painting is very raw, and there is so little image against a broad background," she says. "The spot would still be obvious and the work still unexhibitable."

After puzzling over the restoration problem for a few months, Baxter and her colleague William Real concluded that it would take a rocket scientist to figure out how to make the errant kiss disappear. A pair of rocket scientists, in fact. At an annual conference of the American Institute for Conservation, Bruce Banks and Sharon Miller of NASA's Glenn Research Center in Cleveland proposed that a process they had developed to test materials for use on the exterior of the space shuttle could also restore badly tarnished works of art. With no other alternative than to hide Warhol's "Bathtub" in permanent storage, Baxter and Real were eager to find out more about the technique but were also skeptical about whether it would work. So were a host of other art conservators with vandalized or smoke-damaged masterpieces gathering dust in museum vaults. "These people are not going to try something unless they're up against the wall," says Banks, Glenn's chief of electro-physics. "They're not going to use this weird technique from NASA if they can use their conventional, reliable techniques."

The space-age solution touted by Banks and Miller is atomic oxygen, one of three types of naturally occurring oxygen. Atomic oxygen, found only on the fringes of the atmosphere or in controlled conditions in the laboratory, consists of single atoms. O2, the oxygen we breathe, is made up of pairs of bonded atoms. O2 molecules are relatively stable but can be agents of change when they combine with other molecules in a process called oxidation, producing such phenomena as rust, withered apples, and fire. And O3, or ozone, consists of three-atom molecules created by reactions between O2 and other gases. Ozone molecules are a blessing in the upper atmosphere because they absorb radiation from the sun but are a curse at ground level, where they are a noxious by-product of the gases emitted by cars and industrial sources and are highly toxic to skin and lungs.

In the farthest reaches of the atmosphere, ultraviolet rays split O2 into volatile atomic oxygen that thinly disperses over thousands of miles. "These individual atoms don't have many opportunities to recombine into either ozone or O2 up there," says Banks. "They're like people in a desert. They don't bump into each other because there aren't many of them." Given the opportunity, however, atomic oxygen reacts quickly with other unattached or weakly bonded atoms, such as those in the hydrocarbons within the polymer sheets that hold the space station's solar arrays in place. Without protection, the sheets would disintegrate into carbon monoxide and carbon dioxide gases within a year.

Banks and Miller use a low-pressure chamber in their lab to simulate the atmospheric conditions encountered by orbital spacecraft and then split O2 into atomic oxygen to test the durability of various polymers and protective coatings. Meanwhile, in keeping with the budget-minded mandate at NASA in recent years to spin off space technologies for civilian use, Banks and Miller also frequently work with outsiders. For example, they have conducted commercially funded lab tests that proved atomic oxygen could remove organic contaminants from the insides of headlights or texture the tips of fiber-optic probes. Their involvement in the world of art was prompted by a phone call.

One day Kenneth Bé, a conservator at the nearby Cleveland Museum of Art, contacted the Glenn Research Center seeking advice on how to clean the thick layers of soot off two 19th-century oil paintings rescued from a fire at the local St. Albans Church. Banks and Miller suggested that atomic oxygen might be perfect for restoring the paintings, because soot is just loosely bound hydrocarbons, and the metal oxide paints beneath, already fully bound to oxygen atoms, would be immune to further oxygen attack. Using atomic oxygen, they reasoned, would eliminate any need to rub or even touch the dry and brittle canvases. There was just one problem: The technique had never been tried on an actual painting.

To test their theory, Banks and Miller set up some large-scale burn tests at the Cleveland Fire Department's training facility, where firefighters obligingly burned down mock living rooms decorated with expendable oil paintings. The scientists then placed these smoke-damaged test samples in the low-pressure chamber at their NASA lab and bombarded them with atomic oxygen. True to predictions, the atomic oxygen combined with the soot to produce carbon monoxide, carbon dioxide, and water vapor, which all separated from the paint surface. Banks and Miller were also delighted to discover that the atomic oxygen did not disturb some charcoal markings on the backs of the canvases.

"This is pretty much a line-of-sight cleaning process," says Miller. "The atomic oxygen reacts with the first thing it comes into contact with. If something is around the corner, it won't be affected."

Confident that they could exercise complete control over the process, Banks and Miller loaded the St. Albans paintings into the atmospheric chamber. Gradually, the colors began to emerge, then the details: a lock of hair, delicately arching eyebrows, a floral embroidered sleeve, a rosary, and finally the entire image. "It was remarkable," says Father Bob Weaver, pastor of St. Albans. "The colors were livelier than ever and decades of shmutz were removed along with the soot. We can now see jewelry and the pattern of Mary Magdalene's cape, details we didn't see even before the fire."

The vandalized Warhol painting presented Banks and Miller with a bigger challenge. To begin with, "Bathtub" would be likely to command a price on the open market of several hundred thousand dollars. Despite the successful restoration of the St. Albans paintings, the conservators at the Andy Warhol museum felt reluctant to put the canvas in an atmospheric chamber and expose it to changes in pressure or humidity. So Banks and Miller offered to come to the Warhol Museum and use a handheld device to apply atomic oxygen to selected areas. But before they traveled to Pittsburgh, there was more kissing to be done. Baxter sent some thinly painted canvases to Cleveland, where interns from the Ohio Aerospace Institute donned lipstick and puckered up to the test samples. Time after time, the atomic oxygen combined with the hydrocarbons in the lipstick stains and successfully removed them.

A few weeks later, the scientists and conservators gathered in the nearby Carnegie Museum of Art's conservation lab for one final test. Banks and Miller aimed their atomic oxygen gun at a smudge of lipstick applied to part of the canvas stretched and wrapped around the frame. The process took five hours but was a complete success. So the next day, Banks and Miller returned and huddled around the actual kiss with their equipment as Baxter and Real paced at a distance. "They worked slowly and carefully, almost canvas weave by canvas weave," says Real. "Still, it was very hard for us to stand by."

Finally, Banks and Miller stepped back to show that a corner of the kiss was gone. Like the grin of a ghostly Cheshire cat, the kiss became smaller and smaller as the hours passed, and by the end of the day, it had vanished. "We're ecstatic," says Real. "This is a painting we thought would never again be shown to the public. It's a real triumph."

Success has emboldened Banks and Miller to venture further afield. They're now conducting tests to see whether atomic oxygen can erase soot ingrained in ancient Egyptian tomb paintings by the candle flames of long-gone squatters. They're also experimenting on a chip of paint from one of the most famous works of art damaged by fire a Monet "Water Lilies" charred in a New York gallery in 1958.

Even if atomic oxygen continues to produce impressive results, conservators will most likely yield their precious masterpieces to the NASA scientists only when they have no other choice. For their part, however, Baxter and Real have all the evidence they need: "Bathtub" is once again hanging on the wall of the Warhol Museum. Unfortunately, they already have another opportunity to test the atomic oxygen. At a traveling Warhol exhibit in Vienna, someone embellished two paintings of Liza Minnelli with a felt-tip marker. "We're glad there's this new technology to help us out," Baxter says wearily. "But we sure wish people would stop messing up our art."